A. Field of the Invention
The device of the present invention generally relates to molded case circuit breakers and, more particularly, to structural components thereof configured to provide dimensionally small, sturdy and effective electrical circuit breakers.
B. Description of the Prior Art
Circuit breakers and, more particularly molded case circuit breakers are old and well known in the prior art. Examples of such devices are diclosed in U.S. Pat. Nos. 2,186,251; 2,492,009; 3,239,638; 3,525,959; 3,590,325; 3,614,685; 3,775,713; 3,783,423; 3,805,199; 3,815,059; 3,863,042; 3,959,695; 4,077,025; 4,166,205; 4,258,403; and 4,295,025. In general, prior art molded case circuit breakers have been provided with movable contact arrangements and operating mechanisms designed to provide protection for an electrical circuit or system against electrical faults, specifically, electrical overload conditions, low level short circuit or fault current conditions, and, in some cases, high level short circuit or fault current conditions. Prior art devices have utilized an operating mechanism having a trip mechanism for controlling the movement of an over-center toggle mechanism to separate a pair of electrical contacts upon an overload condition or upon a short circuit or fault current condition. Such trip mechanisms have included a bimetal movable in response to an overload condition to rotate a trip bar, resulting in the movement of the over-center toggle mechanism to open a pair of electrical circuit breaker contacts. Such prior art devices have also utilized an armature movable in response to the flow of short circuit or fault current to similarly rotate the trip bar to cause the pair of contacts to separate. At least some prior art devices use blow-apart contacts to rapidly interrupt the flow of high level short circuit or fault currents. In the design of small molded case polyphase circuit breakers, it is often desirable to have adjacent pole mechanisms spaced closer than adjacent external electrical terminals. Among other advantages, the closer spacing of adjacent pole mechanisms enables thicker and stronger molded case walls to be used. Generally, to achieve the closer spacing of adjacent pole mechanisms, prior art devices used relatively wide lower electrical contacts to compensate for contact misalignment or used separate spacers for shifting the lower electrical contact carriers or used angularly disposed external electrical terminals to compensate for the contact misalignment.
While many prior art devices have provided adequate protection against fault conditions in an electrical circuit, a need exists for dimensionally small molded case circuit breakers capable of fast, effective and reliable operation and, more specifically, for components thereof that provide closer spacing between adjacent pole mechanisms than between adjacent electrical terminals without resorting to the disadvantageous measures referred to hereinabove.